A middle-aged couple, with two beautiful daughters, decided to try one last time for the son they always wanted.
Soon, the wife became pregnant, and, nine months later, delivered a baby boy.
The joyful father rushed to the nursery to see his new son, but was horrified to find an incredibly-ugly baby.
He went to his wife and said, "I cannot possibly be the father of that hideous child. Look at the two beautiful daughters I fathered."

When his wife blushed, he became suspicious, and demanded, "Have you been fooling around on me?"

His wife confessed, "Not this time."